May 1st is typically decision day – the date when students must tell colleges whether they plan to attend. Some colleges are June 1st, but May 1st is the most common. Assuming you’ve decided on a college, double-check that you’re confirmed your attendance by whatever means they require; typically by sending a deposit.
This decision date is most important for selective colleges (which have waiting lists), but non-selective colleges may give your scholarships away if you haven’t confirmed.
Even this date isn’t the end; you still can apply late to many colleges, or change your mind. This would be on a space-available basis, and sometimes with minimal financial aid. We’ve had students who have changed their minds a few weeks before school starts, and it can actually work out. But it sure is easier to make up your mind sooner.